How to establish a dichlor/chlorine dosing routine

[999]

After owning my hot tub for just over 3 months I changed my water and took the opportunity to change from Bromine to granular Chlorine (dichlor 55%).

Straight away I noticed that the smell of chlorine is much better. (personal preference I know)

I need to establish a regular routine dosing with chlorine. It is difficult to know how much to dose and how long it will last.

My tub holds 1700 litres or 450 US gallons and I have an ozonator. We use the hot tub about three times per week, but most of the time it is just me and my wife. Our young kids sometimes get in but not for long.

On the first day of my new water I added 5 teaspoons of granular chlorine and checked the level soon after and found it to be 5 ppm. It then took 24 hours to heat up.

On the second day it was 1-3 ppm.

On day three it was 0. Although we intended to use the hot tub I did not want it to remain at 0, so added 3 teaspoons. (maybe that was too much) This took my level up to 3-5 ppm. About an hour later two of us used the tub. When we got out i threw in another 1 teaspoon. I had planned to does it afterwards but put in a half hearted 1 teaspoon, considering I had already put 3 in earlier.

I don't want to add to much, as this will increase my cyanuric acid levels and reduce the life of my water, but I don't want it going to zero either.

I have obviously got to get into a routine of dosing at the right amount to get me through a couple of days, but also like the idea of dosing after I get out.

I have searched the web for a dosing routine, but there seems to be no hard and fast rule.

I would be interested to know the routine that works for those that use chlorine/dichlor.

[Flyonthewall]

i'm sure you'll get many differing responses on this, but i'll throw my 2 cents in anyways.  our customers that rely on dichlor generally use about 6 teaspoons as a regular weekly dose.  this will vary based on the size of the tub.  as i understand it you want to shock to a level 10 once a week.  we also ask that they use smaller doses during the week after soaking to maintain a level (usually 1 teaspoon per person).  leisure time makes a cool new product called replenish that you could also use after soaking (85% non chlorine shock/15% chlorine).  make sure you flush with spa system flush periodically or you'll find your demand going up due to contaminants in the plumbing.

in almost all cases you'll find that the ph drops when using this method.  make sure you test and adjust it every week.  powdered spa up (identical to baking soda) will be what you normally need.

[Jacuzzi Jim]

  Not sure what spa you have circ pump or not?   But get and use one of those mineral cartridges they work well with chlorine and ozone.  I also like mentioned find it better if your gonna add chlorine do it after use, that way your not sitting in freshly chlorinated water.    While usage varies I add 1 to 2 tblspns of chlorine once a week depending on use shock with 2 tblspns using a non chlorinated shock once a week.  Keep PH/alk in check.  Thats with a couple of kids and 2 adults at various times. 

  I do nuke with chlorine at least once a month to a higher ppm.  I will also do this before a water change to help clean the pipes out.   

[999]

Thanks both. ..... Jacuzzi Jim, i have a Jacuzzi J230CD. It does have a circulation pump. Do you add your chlorine just once a week then?

I have been using non chlorine shock with bromine so intend to use it once a week with chlorine.

[chem geek]

If you weren't using an ozonator, then I could give you a rough rule-of-thumb which is that for every person-hour of soaking in a hot (104ºF) tub, it takes 3-1/2 teaspoons of Dichlor or 5 fluid ounces of 6% bleach or 7 teaspoons of non-chlorine shock (43% MPS) to oxidize the bather waste.  These amounts are independent of spa size.  After that, the FC level drops by around 25% every 24 hours.

With an ozonator, this all changes, but how much depends on the strength of the ozonator and on your soaking pattern.  For a typical ozonator and bather load, an ozonator cuts down the chlorine demand during the soak by about half, but it also roughly doubles the chlorine loss in between soaks (after bather waste is oxidized) to around an FC drop of 50% every 24 hours.

If you have a fairly regular pattern of soaking, then I would just adjust the amount you add after each soak such that you have a 1-2 ppm FC measured residual at the start of your next soak.  For your sequential daily soaks, that would be one amount to add, while for your last soak with a gap a few days before the next soak, you would need to add more unless you wanted to add chlorine in between soaks.

If you wanted to avoid as much buildup of CYA, you could use some non-chlorine shock along with chlorine after your soaks (e.g. Replenish that flyonthewall mentioned) or you could use bleach instead of Dichlor once your CYA is at 30-40 ppm or so, BUT if you use bleach then your water parameters need to be different in order to easily maintain pH (i.e. you need your TA lower at 50 ppm or even a bit lower and you should use 50 ppm Borates).  If you use Dichlor-only or a Dichlor/MPS mix, then this is net acidic so you need a higher TA (usually 80 ppm is OK) for the pH to be stable, but over time your TA will drop so you'll bring that back up with some baking soda every now and then.  With the bleach method, the TA doesn't change once you get to reasonable pH stability.

[Jacuzzi Jim]

Thanks both. ..... Jacuzzi Jim, i have a Jacuzzi J230CD. It does have a circulation pump. Do you add your chlorine just once a week then?

I have been using non chlorine shock with bromine so intend to use it once a week with chlorine.

   Pretty much just once a week, like I said a lot depends on use but yes once a week does work.  I test once a week if that as well.    After you get it down and figure out what works best for you is the key.   Every "body" is different from how much you sweat to how long you stay in.   I also don't shower every time before I get in.  Now if I have been out weedwacking the property for the last few hours than yes, but daily after work as a sales guy no.    Same with the kids during the Summer with sunblock and what not really depends with them, most of the time they just jump in and things are fine.

  Biggest thing I tell people is don't sweat the small stuff, use your eye's as well as your nose and after awhile you will be able to tell if things are going good or going bad but don't neglect it either! 

[999]

I'm only on day 5 of using chlorine (having changed from bromine) and seem to be struggling.

My chlorine demand seems high. I have already put 12 teas spoons in. (or 4 tablespoons) and on two mornings I have found that my readings are zero. My wife and I have only used the hot tub once.

Day 1 put 5 tea spoons bringing level up to 3-5 ppm
Day 2 didn't put anything in and level was 1-3 ppm
Day 3 level was 0 ppm so put in 3 tea spoons, used the tub then put in another 1 tea spoon
Day 4 level was 2 ppm so i added 1 tea spoon to bring it up to 3 ppm
Day 5 level was 0 ppm, so I have added two tea spoons (we intend to use it tonight so will add another 2 tea spoons after)

I am fairly certain that I don't have a bacteria problem considering that I run the tub successfully for three months on bromine and then used Swirl Away before the water change.

I know that I have a Coroner Discharge Ozonator. This was an optional extra for my tub. Is it this that is driving my chlorine down.

At this rate I will be using about 19 tea spoons per week and that is with low usage (twice). It wont take long for my CYA to build up and then need a water change. I could hit 100 CYA in 6 weeks.

[chem geek]

Day 1 put 5 tea spoons bringing level up to 3-5 ppm

5 teaspoons in 450 gallons would be 7.7 ppm FC so if you measured the chlorine level before and shortly (say within 10 minutes with the circulation pump on) after dosing and it only went up 3-5 ppm, then something is wrong, possibly with your measuring spoon.  Are you using an accurate test kit or are you using test strips?

I know that I have a Coroner Discharge Ozonator. This was an optional extra for my tub. Is it this that is driving my chlorine down.

At this rate I will be using about 19 tea spoons per week and that is with low usage (twice). It wont take long for my CYA to build up and then need a water change. I could hit 100 CYA in 6 weeks.

If you don't have bacterial growth or biofilms, then it could be the ozonator that is reacting with a lot of chlorine.  Typical ozonators increase chlorine demand to around 2 ppm FC per day.  19 teaspoons per week in 450 gallons would be about 29 ppm FC per week or about 4 ppm FC per day.  2 people soaking for 30 minutes (so 1 person-hour) would consume around 3-1/2 teaspoons of Dichlor so the rest of the demand is 3.4 ppm FC per day which seems high even with an ozonator though I suppose is possible if your ozonator is powerful and on a lot.  If you turn off your ozonator, that would tell you if it is the cause of your more rapid chlorine loss.

As for the buildup of CYA, note that most chlorine spa users use only Dichlor and just live with the fact that they have to change their water sooner than they otherwise would.  You could completely avoid that problem by switching to bleach after the CYA level gets up to 30 ppm or so, BUT to use bleach you have to take other steps to have the pH be more stable (namely, have a low TA of 50 ppm and use 50 ppm Borates).  Also, this won't solve the chlorine demand problem you have that may be due to the ozonator.

An ozonator is more appropriate for spas used more frequently, every day or two, or for bromine spas to keep a bromine residual without needing bromine tabs, though the ozonator needs to not be too strong or else the bromine level will be too high.

[999]

My ozonater is hard wired into the control box and good seem s to be on 24/7. There isn't a switch to turn it off.

As for my initial dose of 5 teaspoon. It was on the high side, so could have been higher than 5.

I do use Insta test strips that seemed fine with using bromine but i do rely on them to give an accurate reading. If i get an extreme reading i take another with some Jacuzzi strips. If they read the same them i figure it is correct.

Used the tub last night, two of us for 40 minutes. Before we got in there was 1ppm and i added two tea spoons when i got out. This morning, 11 hours later it was reading 3ppm. Hopefully there wil still be something left by this evening.

I know it is early days but if i am going to be constantly adding chlorine and a lot of it, i may change back to bromine and just put up with the smell.

[Jacuzzi Jim]

My ozonater is hard wired into the control box and good seem s to be on 24/7. There isn't a switch to turn it off.

As for my initial dose of 5 teaspoon. It was on the high side, so could have been higher than 5.

I do use Insta test strips that seemed fine with using bromine but i do rely on them to give an accurate reading. If i get an extreme reading i take another with some Jacuzzi strips. If they read the same them i figure it is correct.

Used the tub last night, two of us for 40 minutes. Before we got in there was 1ppm and i added two tea spoons when i got out. This morning, 11 hours later it was reading 3ppm. Hopefully there wil still be something left by this evening.

I know it is early days but if i am going to be constantly adding chlorine and a lot of it, i may change back to bromine and just put up with the smell.

  Some here will prolly disagree, but you don't always have to have a chlorine reading 24/7 just be sure to hit it once or twice a week and you should be fine.    And like you said if your constanlty adding chlorine to keep a level up might as well go back to bromine in my opinion.    Thats exactly why I like ozone and proclear (nature2 cartridge) And if for now you want to error on a safe side just add 1 tblspn or less of chlorine after use.  You will be fine!   Also your ozone is not on 24/7 anytime you hit a main pump btn your ozone will shut off and then come back on after the pumps have been shut down for awhile.     Also test strips are not quite as accurate as a test kit with the drops. 

[999]

I don't think i could use the cartridge that you mention because my filter doesn't have a centre section that comes off. It is fixed.

I am encouraged to know that there doesn't have to be a constant reading of chlorine.

My ozonator is always bubbling, even with the pump on.

[Jacuzzi Jim]

I don't think i could use the cartridge that you mention because my filter doesn't have a centre section that comes off. It is fixed.

I am encouraged to know that there doesn't have to be a constant reading of chlorine.

My ozonator is always bubbling, even with the pump on.

  You can just lay the cartridge in the basket as long as it has some water flow across it it will work.    Worth a shot.

[999]

What 'basket' are you referring to. Is this the netting bag in front of the filter oe do you mean behind the filter panel alongside the filter.

If i was to use one of those cartridges as well as ozone, i presume you still use chlorine but less if it?

[999]

Just read the instructions for Nature2 and it says you have to use MPS with it to work. That is another addition that i don't really want to keep adding. I will see how i go with chlorine for the next week. If it proves problematic I will go back to Bromine.

[Jacuzzi Jim]

  Sorry I was thinking older J-230.  You can just put the nat 2 in the netted bag.   MPS is basically your shock which you will be using in conjuction with chlorine.     Some people will use MPS (shock) after each soaking as well.  and chlorine once to twice a week.  Really varies on use and number of people.